We have developed a cryogenic probe and cryostat system to test both active and passive superconducting devices and circuits up to microwave frequencies at variable temperatures. Our system consists of two basic parts: the cryostat and the matching probe. The cryostat is a unique, very efficient, variable temperature, flow-type cryostat, where we control temperature without electrical heaters. It is magnetically shielded and allows rapid testing between 4.2 K and room temperature. Probes developed for this cryostat have a larger number of shorter cables than standard dip-type probes. They are designed to test chips or chip assemblies without additional packaging. Chips or chip assemblies can be quickly mounted and dismounted from a fixed spring-contact assembly. Each probe has 56 wide-bandwidth signal cables. We have repeatedly used these probes for testing both active and passive superconducting integrated circuits up to 20 GHz. The probe and cryostat combination provides a testing capability that is simultaneously high frequency, dc magnetic shielded, has variable cryogenic temperature, and quick turnaround.
We have developed a cryogenic probe and cryostat system to test both active and passive superconducting devices and circuits up to microwave frequencies at variable temperatures. Our system consists of two basic parts: the cryostat and the matching probe. The cryostat is a unique, very efficient, variable temperature, flow-type cryostat, where we control temperature without electrical heaters. It is magnetically shielded and allows rapid testing between 4.2 K and room temperature. Probes developed for this cryostat have a larger number of shorter cables than standard dip-type probes. They are designed to test chips or chip assemblies without additional packaging. Chips or chip assemblies can be quickly mounted and dismounted from a fixed spring-contact assembly. Each probe has 56 wide-bandwidth signal cables. We have repeatedly used these probes for testing both active and passive superconducting integrated circuits up to 20 GHz. The probe and cryostat combination provides a testing capability that is simultaneously high frequency, dc magnetic shielded, has variable cryogenic temperature, and quick turnaround.
We demonstrate a packaging system/test probe suitable for testing complex, large scale superconducting integrated circuits with thousands of Josephson junctions. The cryopackage is designed to work with a 1 cm superconducting die, with liquid He immersion cooling using a standard storage dewar. The package has 80 high-speed input-output lines (DC to 20 GHz) which connect the chip to room temperature electronics. The tip of the cryopackage, containing the chip, is shielded from the ambient magnetic field with two mumetal cylinders and contains a built-in coil, which provides in-situ degaussing of the inner shield. To clear flux trapped in the chip being tested, the probe contains a novel gas manifold and a system of heaters. During the defluxing operation, a heater evaporates liquid helium inside the chip enclosure, the expanding vapor purging the liquid from the sample cell and warming the chip above its transition temperature. Once the chip is defluxed, the liquid helium is allowed back into the cell, at a rate slow enough to avoid trapping flux in the chip while it is cooled. The process can be automated and does not require any movement of the probe once inserted in the dewar.
Integrated semiconductor circuits operating at cryogenic temperatures can play a crucial role in scaling quantum computing architectures based on trapped-ion and superconducting qubits. Other technologies, such as low-temperature detectors, can also benefit significantly from these circuits. These applications demand high-frequency, cryogenic temperature measurement systems for the thorough characterization of semiconductor components and circuits. This work presents a customizable, high-frequency, fast, and reliable cryogenic measurement setup for measurement temperatures ranging from room temperature to 4.2 K. It features up to two dc probes or two ground-signal-ground probes for frequencies of up to 67 GHz, which can be configured in a 180° or 90° configuration. In addition, up to 48 BeCu wires configured as twisted pairs provide supply and control signals. Furthermore, up to four rf connections can be mounted directly to a printed circuit board. The setup features an optical microscope in the vacuum chamber to position the probes, which is further utilized by a machine vision algorithm, allowing the detection of pads and automatic positioning of the probes over the pads. The hardware is located in a 550 × 500 × 500 mm3 large vacuum chamber with two independent pulse tube cryocoolers with cooling powers of up to 0.9 and 0.4 W at 4.2 K. Exemplary room temperature and cryogenic S-parameter, transient frequency (fT), time-domain, capacitance-voltage, and dc measurements of single transistors and integrated circuits fabricated by Infineon are presented, demonstrating the system's measurement capability for quantum computing and other applications.
NbN RSFQ circuits operating at 9 K reduce the cooling constraints especially for portable, remote, telecoms or medical imaging applications. We have developed a test-bed to study the operating temperature of the various mixed RF and digital circuit blocks of NbN ‘HyperSCAN’ project test vehicle 1cm2chips. The use of a widespread helium cryostat (‘Orange-ILL’) allows us to stabilize the chip temperature in the range 2.9 K–20 K with thermal oscillations lower than 0.1 K. The chip is mounted on a PCB and shielded from the external field: the PCB provides a multi-connection packaging used in order to study temperature and frequency operation of 30 GHz NbTiN CPW filters, RSFQ gates, analog SQUID and NbN/TaN/NbN SNS junctions arrays. The comparison between electrical simulations and tests is made on flexible,$\sim56cmlong,micro−striplineribboncablecarrying32signalseachincludingbiaslines,intherangeofDC−3GHz,combinedwith4semi−rigid\sim$40 GHz coaxial cables. By removing spurious resonances, it is expected to take full benefit of the large bandwidth, low insertion loss and low thermal conductivity of the set-up. We emphasis on the flexibility, large yield, reliability and reduced cost of such packaging coupled to He cooling exchanger for applying to testers and to future 9 K NbN multi-ADC green and remote systems when only low electrical power sources are available.
This paper describes a cryogenic multi-chip module (MCM) probe for testing of a superconducting hybrid digital signal processor (DSP) capable of 24 giga multiply accumulate operations per second. The probe has 39 data channels with 4 GHz bandwidth, a 30 GHz high speed clock input line, and 48 biasing lines. The MCM interface board features 164 spring finger contacts for a 30 times 30 mm2MCM. The probe has low heatload (0.23 W) and provides good magnetic shielding with residual field equal to 250Phi0over a 5 times 5 mm2area. The measured time skew between 20 of the 1200 mm data coaxial lines is about 70 ps. The probe allows synchronous data word transmission at 2 Gbps.
A noncontact cryogenic microwave measurement system has been developed for the characterization of passive and active superconducting devices by means of an unloaded quality factor measurement technique. The measurement system was designed specifically for the characterization of planar thin film resonant structures as a function of temperature (4–300 K), frequency (100 MHz–26.5 GHz), and dc voltage bias (≤100 V). It has been used for basic device studies of novel active superconducting lumped components made of metal-oxide superconductor/insulator heterostructures.
Future development of superconductor digital and mixed-signal ICs requires extensive testing with a large number of input/output (I/O) lines for applying independent bias controls, injecting test signals, and monitoring outputs of different sub-circuits. There is a growing need for a standardized test apparatus for a variety of complex superconducting chips and multichip modules (MCMs). Such a test apparatus must support many I/O lines, be easy and cost-effective to operate, and support prolonged automated testing. Existing test apparatus include liquid He cryoprobes and cryocooled custom digital-RF systems, both of which have drawbacks. Liquid He cryoprobes with universal wiring, such as 40 or 80 coaxial cables, are convenient to use. Cooled by immersion in a tank filled with liquid He, these cryoprobes allow rapid cool-down and warm-up. However, large consumption of liquid He, the cost of which has been steadily increasing worldwide, makes this solution rather expensive and wasteful. On the other hand, one can exploit the modular reconfigurability of HYPRES' digital-RF receiver product to create a testbed for different ICs. Such a system uses the smallest commercially available closed-cycle refrigerator (~1.2 kW) and has negligible operating cost. However, reconfiguration takes time and expertise since these products are specially designed with customized chip package and wiring to minimize the thermal load on the cryocooler. These low-maintenance systems are ideal for prolonged operation of a single chip, which is invaluable for superconductor electronics system developers and end-users. The integrated cryoelectronics testbed (ICE-T) combines the advantages of the liquid He cryoprobe and the cryocooled digital-RF product. By using a more powerful, commercially available, electrically powered closed-cycle refrigerator (7 kW), ICE-T alleviates the thermal constraints on wiring while maintaining very low operating cost. By separating the electrical and thermal subsystems, it maintains modularity without sacrificing the universality of the cryoprobe. A set of universal and custom electrical modules can be independently built and inserted in ICE-T. Universal inserts with 40 and 80 coaxial cables accommodate all chips with standard I/O pads like the familiar liquid He cryoprobes. Custom inserts for different classes of chips and MCMs are designed and built according to user requirements and specifications. The utility of the ICE-T was successfully demonstrated by testing a benchmark superconducting digital circuit at low frequency and an analog-to-digital converter chip clocked above 20 GHz.